Just a few hours ago police in New Zealand shot a twelve foot shark as a tore part of swimmer. At a popular surfing beach and witnesses reportedly saw other sharks circling. For the big one attack. After a smattering of great white sightings off the eastern seaboard -- this country last summer. That is a kind of story that strikes reasonable fear but while many see big sharks as monsters. Those who study didn't see amazing -- -- predators vital to ocean health. One team determined to discover what makes them tick what brings -- close. At that ABC's Lindsey Davis goes along the trail of the great why. There are fifteen adrenaline -- minutes. That's the maximum time his team tested tank test in relief isn't massive 3500 pound lion of the city. First they cover eyes and give her a water supply. The next bit of poking and prodding allows them to draw blood and run a battery of tests -- little -- out -- then comes the moment that could change. Time when it comes to understanding great whites they insert a homing device into that signature dorsal fin. Essentially built teen GPS that -- -- -- the satellite capable of tracking and monitoring the movements of the sharks. Anywhere they go in the world. The -- -- go I -- undermanned the F my mother. Because my parents have done so much I was just waiting and waiting for a special shark. To name after her. Whoa that's an airline the Manning charge juvenile is Chris Fisher -- spends his lying fishing for great white sharks -- learn more about. -- -- He invited us on board his ship -- -- he spends most of his days trying to crack the shark code. As a result of his work each month a million people check his global shark tracking web site. To follow the sharks -- tank from Florida all the way up to new England and beyond. It is cruising along a -- -- the Empire State Building and it just. New Yorkers don't -- this thing about sharks. That just off the coast here there's Denton and and yes you're. -- and they live here. With John Stephen Spielberg's single handedly inciting terror about what could be lurking close to sure. Now almost forty years later -- trying to dispel some of that fear and mystery by putting great whites on the neck. Literally are -- coming closer. And then they used it nobody knows what. They used to do this is the first time were establishing these tracks understand what normal -- even is. People say well what's Mary Lee do -- -- -- cruises up the southeastern coast of the United States fact is we don't really know. See this little orange dot. That's Mary Lee she is one of two North Atlantic great -- T caught in September just off the coast of Cape Cod. Bailey's track is a perfect example of why people don't really need to be worried about -- -- -- swimming she has -- the entire lying. -- eastern seaboard on the beach. In the past six months she's traversed the -- the East Coast hugging shoreline from Massachusetts. To Jacksonville Florida. I had to call the authorities in Jacksonville beach. Because -- -- us live right in look at this isn't a hundred yards other surf spot in a public here. She then went back up to Rhode Island and was most recently spotted in the vicinity of Bermuda. Some environmentalists suggest that what you're doing is too invasive than it actually harms the shark we have the data now to understand that it's not that much stress there's no time. What -- -- gonna sit back and -- about this for another day and let another 200000 defense. The real outrage according to Fisher should be -- images like this rooftop in Hong Kong. Covered in thousands of freshly sliced -- -- Think about all the carcasses strewn -- on the bottom of the innocent their -- was just for that one rooftop. These fans are then used to make a soup viewed by many Asians as a rare delicacy. You can't remove the apex predator from the ocean for a bowl of soup and expect the ocean have a robust future. Fisher has joined forces with Greg's -- the marine biologist and one of the stars of discovery channel's shark week. The pianist -- and fish are using a different technique. They successfully managed to -- munition -- not far off the beaches of Cape Cod. It's amazing and he told -- four years ago that we be able to attack this many white sharks I would have said -- you're right your mind. What can cause such a -- mom and my guess is that jacket kinds of breeding site. I believe they'll be -- and -- early winner but that's just my guess based -- -- -- -- around the world. Does sex does or does hired as a contender while a great deal of his research appears to be uncharted territory he believes breeding is large. -- -- drives a lot of their yeah. Now the map on your left here for the mature female sharks. And the map on the right here is the mature male sharks and usually -- -- mature females in the mature males coming together as a reason and it doesn't want to rocket scientists -- Ph.D. to figure out maybe that is the green side. Well these sharks -- the largest predatory fish on earth should says they've been given a bad rap. It's a more dangerous to drive to the needs them to go swimming in the action. We are hooked up hooked up. With this team's ground breaking research they're hopeful they'll make some -- -- -- people's fear of sharks with curiosity. For Nightline I'm Lindsey Davis in New York.

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